Effect of acylation on substructural properties of proteins: a study using fluorescence and circular dichroism

Abstract

Effect of succinylation, acetylation, and reductive alkylation on substructural properties of three milk protein systems (casein, BSA, and whey proteins) was studied. Three levels of modifications were achieved in each case, and changes in the proteins' spectral properties were determined. Casein attained the highest degree of modification for all of the treatments used. Acylation enhanced denaturation and improved surface hydrophobicity of all of the proteins. Modification of BSA resulted in a red-shifted emission fluorescence peaks; however, its circular dichroic (CD) patterns showed insignificant difference from those of the native. This may imply that acylation has affected only the tertiary structure of BSA. Fluorescence and CD profiles of whey proteins and caseins showed considerable changes in their conformational makeup. It appears that acylation may have a more drastic effect on multicomponent proteins, possibly by means of perturbing their protein-protein mode of interaction.

Application Potential of Food Protein Modification

“…Large extents of succinylation have been reported to affect the integrity of secondary and tertiary structure of soy protein hydrolysate as shown by intrinsic tryptophan fluorescence and circular dichroism (Achouri & Zhang, 2001). Similar conformational rearrangements have been reported upon succinylation of whey protein isolate (Gruener & Ismond, 1997), bovine serum albumin (Jonas & Weber, 1970), canola protein (Lakkis & Villota, 1992), Faba bean legumin (Schwenke et al, 1998), rapeseed 12S globulin (Gueguen et al, 1990), and winged bean protein (Narayana & Rao, 1991). As a result of co-incubation of soy protein hydrolysate with succinic anhydride, which is a common compound used to succinylate proteins, heterogeneous reaction mixtures were obtained.…”

Molecular Characteristics of Bovine Serum Albumin-Dextran Conjugates

“…The fluorescence intensity is proportional to the amount of ANS bound to the hydrophobic surface region. 33) In this study, the amounts of ANS bound to each conjugate were similar because the fluorescence intensities of the conjugates were not significantly different. These results suggest that the distribution of the hydrophobic surface regions, which had affinity for ANS, was similar in each conjugate.…”

Modifications of structures and functions of caseins: a scientific and technological challenge

“…According to Lieske (1999), there is also a calcium depletion for the succinylated casein micelles, a decrease in their surface hydrophobicity, and an increase of their diameter. Lakkis and Villota (1992) reported spectral changes of fluorescence and circular dichroism of caseins after their succinylation.…”